6th US-PRC Magnetic Fusion Collaboration Workshop San Diego, July 10-12, 2012
Physics Rationale and Engineering Design of Keda Torus eXperiment
Wandong Liu, on behalf of KTX team
School of Physical Sciences University of Science and Technology of China
Collaboration with： – Institute of plasma physics – University of Wisconsin at Madison, U.S. – South western institute of physics – Consorzio RFX, Padova, Italy – Huazhong University of Science and Technology – Kyoto Institute of Technology, Japan – University of California Los Angles, U.S. – University of Saskatchewan, Canada A new RFP program started in China
The new reversed field pinch（RFP） program in China, Keda Torus eXperiment （KTX）officially started by the Ministry of Science and Technology, in the framework of the ITER domestic program The duration of the program is 3 years, starting from the end of last year for design and construction of the machine (2012-2014) The University of Science and Technology of China (USTC) will provide a new building to accommodate KTX device Reversed Field Pinch: an important alternate toroidal concept
Three major configuration of MCF
Stellarator: magnetic field is generated totally by the external coils Tokamak: magnetic field is generated primarily by the external coils RFP: magnetic field is generated primarily by the plasma current Tokamak RFP Main advantages of Reversed Field Pinch Small externally applied field:
the use of normal magnets, high engineering beta, high mass-power-density, efficient assembly Large plasma current density: Ohmic heating for a burning plasma Fascinating phenomena of self-organization and nonlinear plasma physics:
test bed for the understanding derived at high field, good platform to investigate the transport, link between the fusion energy science and astrophysics Diversified fusion research recovered
4 tokamaks (EAST/HT-7/HL-2A/J-TEXT) a small spherical tokamak (SUNIST) a reversed field pinch (KTX) Spherical Tokamak SUNIT @ THU
Tokamak EAST & HT-7 @ IPP Beijing RFP KTX @ USTC Hefei Chengdu Tokamak Wuhan HL-2A @ SWIP
Tokamak J-TEXT@HUST The former RFP research in China
Construction from 1985 running from 1989 Shutdown in 1997 R=0.48m, a=0.1m air core Al shell: d=1cm stainless steel liner: d=0.4mm plasma pulse < 2ms,
Ip~150kA(max) Te~100eV
The first RFP device in China :SWIP-RFP Present RFP experiments
RFX-Mod @ Italy • plasma current~2MA, the biggest RFP device, active feedback control, high current operation MST @ U.S. RFX-Mod (Italy) Extrap-T2R (Sweden) R/a = 2 m / 0.46 m R/a = 1.24 m / 0.18m • plasma current ~0.8MA, current drive & confinement improvement Extrap-T2R @ Sweden • active feedback control of the MHD modes Relax @ Japan MST (UW-Madison) RELAX (Japan) • R/a = 1.5 m / 0.5m R/a = 0.5 m / 0.25m small aspect ratio R/a~2
MST: improved confinement achieved via modification of the current profile Recent achievements in RFP
RFX: self-organized Single Helical Axis state come with electron transport barriers Keda Torus eXperiment (KTX) in USTC
In USTC, we have kept fusion research, small-scale but steadily growing, for almost forty years – tokamak physics and diagnostic – fundamental research in small devices: magnetic reconnection experiment, chaos, turbulence… – space plasma research: data analysis and numerical simulation of reconnection phenomena… – theory and numerical simulation: tearing mode, kink mode RFP naturally fits our current status – the diversity of Chinese fusion research • KTX will not only address the relative important scientific issues of Tokamak, but also improve the understanding of toroidal confinement in general – the richness of physics: dynamo, magnetic self organization, RWM – training of fusion talents is the priority of university • The easy operation, compared with Tokamak; daily running The KTX project is a nature extension of China MCF program! Main parameters of KTX
Major radius 1.4 m Minor radius 0.4 m Thickness of vacuum shell (SS) 6 mm (τ ~ 2ms) Thickness of conductive shell (copper) 1.5 mm (τ ~ 20ms) Plasma current 0.5MA (Phase I), 1.0 MA (Phase II) Pulse length 30 ms (Phase I), 100 ms (Phase II) Loop voltage 10～50 V Plasma inductance ～ 4 μH Total magnetic flux 3 ~ 5 V٠S Electron temperature 600 ～ 800 eV Plasma density ～1019 m-3 Maximum toroidal field 7000 Gauss The structure of KTX
Toroidal Coil
Equilibrium Coil
Ohmic Coil KTX has modular shell structure
Thin simple modular shell structure: thin stainless steel shell (6mm thick, 2ms penetration time) and copper shell (1.5mm, 20ms) – close proximity to the plasma – available active controls, e.g., MHD or PPCD & OFCD – potential research for advanced plasma-facing materials, e.g., lithium Double-C structure – ensure an excellent accessibility to the internal space
horizontal gap Stainless steel shell Copper shell
vertical gaps vertical gaps The modeling of KTX performance
500 kA ramped mode
Simplified electrical circuit model
∂W = VI+− VI P ∂t zz θθ Ω
Current profile: Alpha model
α Jr⎡⎤⎛⎞ ==μλ0 ⎢⎥1 −⎜⎟ Ba⎣⎦⎢⎥⎝⎠ collaborated with Prof. John Sarff Design for KTX Ohmic coils
The parameters of Ohmic coils
The mutual inductance of Ohmic coils
Ohmic coils are grouped into 8 sections. The parameters of ohmic coils are optimized to minimize the stray field in the chamber. contributed by Binjia Xiao & EAST team Design for equilibrium of KTX
The parameters of equilibrium coils
Similar to the configuration of RFX, the equilibrium coils of KTX are divided into eight sections, which connect to the corresponding Ohmic coil sections in parallel. contributed by Binjia Xiao & EAST team Design of power supplies (capacitor banks)
The current waveforms TF Coil
TH2 TH1 TFcoil_L 12m H D1 C2 C1 TFcoil_R C3 50u F 3m F 1 F 15k V 40k V 150m Ohm 450 V
Power supply for the toroidal coils TH1 M 96u H D3 D2 Roh D1 9.2m Ohm C3 C2 C1 Lplasma Loh Rplasma 0.15 F 6m F 1.2m F 3.4u H 18.4m H 30u Ohm 5k V 25k V 50k V
Power supply for the Ohmic coils
contributed by Dr. Peng Fu & EAST team Design of KTX machine
Fully design for KTX machine, global shape, vacuum chamber, supporting structure, assembly strategy, analysis… contributed by Dr. Yuntao Song & EAST team KTX Schedule Laboratory building and KTX hall
30×20×16m3 KTX is open for international collaboration
RFX, April 2010 2010 Oct, USTC
Madison, July 2010 June 2011, USTC Summary The features of KTX: – thin simple modular shell structure: good proximity, possible plasma facing material research, easy active control, for PPCD & OFCD research; for single helicity mode research … – double C structure for easy accessibility – capacity for tokamak operation (low toroidal B and q value) The mission of KTX: – contribute to the development of the RFP fusion concept – contribute to fusion science and to explore the similarity (or contrast) to the tokamak configuration – general plasma science (dynamo, reconnection, …) – education and training of fusion scientists Future of KTX in USTC 天时 （right time） – ITER era 地利（right place） – USTC, Hefei, Center for MCF research in China 人和（ harmonic human environment） – Support from international RFP community and Chinese MCF community
Conclusion: KTX must have a bright future Thanks, and Welcome to USTC!